Wind turbines for producing electricity typically use slender turbine blades extending radially from a hub. The hub is mounted to a shaft which drives a generator. Wind turbines are made larger and larger, and the static and dynamic loads on the turbine blades therefore increase.
In blade testing, static loads may be useful for evaluating stiffness and ultimate strength of a turbine blade. However, in practice, the load on a wind turbine blade varies constantly and to evaluate fatigue resistance of the blade, a cyclical load may be applied in large test facilities.
During a typical test, a heavy load rotates eccentrically. The load is strapped to the blade at a location between the hub end and the tip end of the blade and therefore makes the blade oscillate.
Unfortunately, the rotating mass and the oscillating blade requires very large heavy duty building facilities due to the very large forces which are transferred into the floor and other building components during the oscillating movement of the very heavy components.
The wind turbine industry requires a cost effective and convenient method to test large wind turbine blade in fatigue to improve reliability in design and manufacture.
As the size of wind turbine blades increases, the fatigue test rigs require foundations that are expensive and time consuming to construct. In addition, wind turbine blades are now manufactured in many locations around the world and transportable test rigs capable of testing blades where they are manufactured are requested in an attempt to reduce transport costs and save time
It is also desirable to reduce the impact of the test equipment on its ambient environment, for example, load on the building in which the test equipment operates, etc.